The Romance of Modern Chemistry

CHEMISTRY OF THE STARS division is not apparent with an ordinary spectroscope, and need not concern us here. Suppose now we were to introduce into the Bunsen- burner flame some other salt of sodium—washing soda, for example—we should get exactly the same spectrum. This is a fact of the greatest significance, indicating that whatever be the form in which sodium is introduced into the non-luminous flame, its presence is invariably marked by the yellow line at a definite position in the spectrum. From this simple case the reader will easily appreciate the power of detection with which the spectroscope equips the chemist For if the question arises whether a given substance contains sodium or not, he has but to introduce some of it into a Bunsen-burner flame and see whether that incriminating yellow line appears in the spectrum. It has actually been found that as little as one ten- millionth of a grain of a sodium salt can easily be detected in this way. Other incomplete spectra, generally more complex than that of sodium, are observed by introducing salts of various metals into the non-luminous flame of a Bunsen burner (see Fig. 11). Barium salts, for example, impart a green colour to the flame, and their spectrum is charac- terised by a number of green lines ; strontium salts, on the other hand, tinge the Bunsen flame a brilliant crimson, and their spectrum contains a series of lines and bands mostly at the red end. It is probable that every reader, perhaps without knowing it, has seen the colours which barium and strontium salts impart to a flame, for the green and red lights which figure so largely in firework displays are produced by adding these salts to combustible mixtures containing sulphur. For the detection of sodium, barium, or strontium the 208